1. Field of the Invention
The present invention relates generally to automatic side hinge door openers and, more particularly, relates to clutching and braking systems for use in conjunction with automatic door openers suitable for both original installation and easy retrofit onto standard side hinge doors.
2. Related Art
U.S. Pat. No. 5,878,530 to Eccleston et al, dated Mar. 9, 1999 and entitled “Remotely Controllable Automatic Door Operator Permitting Active And Passive Door Operation”, discloses a remotely controllable automatic door opener for a side-hinged door. The opener comprises an electronically operated clutch in the gear train between the motor shaft and the opener arm drive shaft (output shaft). An electronic control unit comprising adjustable timers is employed to govern the opening and closing of the door.
U.S. Pat. No. 5,881,497 to Borgardt, dated Mar. 16, 1999 and entitled “Automatic Door Opener Adaptable For Manual Doors”, discloses an automatic door opener that employs a slip clutch in the drive train between the motor and the output shaft.
U.S. Pat. No. 6,002,217 to Stevens et al, dated Dec. 14, 1999 and entitled “Door Operating System”, discloses a door operating system that employs a dual position feedback system that can help prevent overtravelling of the door when it is being closed.
Other automatic door openers are directed towards opening of garage doors by means of drive chains or worm gears. While such door openers typically have some form of clutch mechanism, the weight of the garage door and the necessity that the garage door be raised vertically on rails require a slip clutch of great torsional capacity and some switching mechanism to stop the motor or interrupt the drive train when the door encounters an obstacle. In such garage door openers, the driven clutch mechanism is a shaft or gear engaging a travel nut or chain.
For example, U.S. Pat. No. 4,334,161 to Carli, dated Jun. 8, 1982 and entitled “Centrifugal Switch And Motor Control”, discloses a friction clutch which is best seen in FIG. 1 and is described in column 2, line 62 through column 3, line 5. The friction clutch includes a circular drive member 27, a driven member 28 and a clutch facing 33 located therebetween. The clutch facing 33 is washer-shaped and has apertures that are slidably received on bosses 34 located on the driven member 28. Another washer-shaped component, hard metal disc 35, is secured by staking 36 to the circular drive member 27 and frictionally co-acts with the clutch facing 33. Tension on the driven member 28 is varied by tightening or loosening a nut 42 which maintains a spring 43 adjacent to the driven member. In operation, the door will move under normal operating conditions but may slip upon a definite overload. For example, should the door strike some obstacle or reach the up or down travel limits, the driven member 28 will stop and, in turn, the friction clutch will slip. When the clutch slips, a centrifugal switch mechanism 47 located on the driven member 28 closes, thereby shutting down the motor. Driven member 28 is connected to output shaft 40 which engages partial nut 45 to pull the weight of garage door 13 up track 14. In this arrangement, the clutch (un-numbered) is not by itself a sufficient safety mechanism should the door strike an obstacle such as a human being, thus necessitating centrifugal switch mechanism 47.
U.S. Pat. No. 3,955,661 to Popper et al, dated May 11, 1976 and entitled “Apparatus For Opening And Closing Door Members And The Like”, discloses an apparatus for opening and closing doors including a ball drive assembly 56. The ball drive assembly 56 provides a driving connection between the driver shaft 50 and a driven shaft 58 such that the driven shaft 58 is rotatably driven at a predetermined reduced rate of speed compared to the speed of the driver shaft 50. A torque control 90 (best seen in FIG. 3) is provided to sense an obstruction in the path of the door member 14 and to send a stop signal to the motor control 48 via signal path 92. As drive chain 16 must vertically raise door member 14, ball drive assembly 56 provides a substantially increased internal friction as compared to the usual coupling devices such as pulley-belt drives or the like, thereby increasing the amount of force which must be manually applied to the door member 14 to move the door member 14 from a stopped or parked position (column 15, lines 17-28). Popper et al emphasize that the ball drive assembly 56 allows for substantially weaker torque control springs 206 and 210, and thus a more sensitive torque control 90. Torque control 90 shuts off the motor in response to the door member 14 being unable to move.
U.S. Pat. No. 5,222,327 to Fellows et al, dated Jun. 29, 1993 and entitled “Side Mount Garage Door Operator”, discloses a side mount garage door opener including a means 17 for selectively connecting and disconnecting the drive shaft 14 with the door opening and closing mechanism 16. A clutch 22 is interposed between the drive shaft 14 and mechanism 16 and is manually operable for disengaging the drive motor from the garage door via a selector member 23 in the absence of electrical power. As illustrated in FIG. 3A, the clutch is shown in the engaged position but may be moved to the disengaged position as illustrated in FIG. 3 via movement of the selector member 23.
U.S. Pat. No. 3,719,005 to Carli, dated Mar. 6, 1973 and entitled “Door Operator Reversing Control”, discloses a door operator having a friction clutch (un-numbered) and a one-way clutch 70. The friction clutch is similar to the one described above with respect to the aforementioned U.S. Pat. No. 4,334,161, and includes a clutch plate 24 and clutch disc 25 carrying a clutch lining 26 which frictionally cooperates with the clutch plate 24. The one-way clutch 70 is provided for moving a torque switch means 48 in one particular direction. A torque weight 71 is slidably mounted in an eccentric aperture 72 in a hub bracket 34 and functions, when the motor is reversed, to drive an inner cylindrical surface 79 of a drive disc 45 to establish a particular position of the torque switch means 48. The torque switch means 48 is moved in the opposite direction by a gravity-actuated weight 68. As in U.S. Pat. No. 4,334,161, worm 17 rotates to raise garage door 12.
U.S. Pat. No. 3,059,485 to Bohlman et al, dated Oct. 23, 1962 and entitled “Electro-Mechanical Door Opening And Closing Mechanism”, discloses a garage door opener as illustrated in FIGS. 1 and 3, having clutch plates 51 and 60 disposed on each side of one wheel 55. Friction plates 65 convey torque to clutch plates 51 and 60 from one wheel 55, which in turn meshes with worm 77 (FIG. 4) situated on shaft 78 of motor 79. Driven shaft 24 is attached to clutch plates 51 and 60 and in turn rotates drum 30 having two runs of cable (un-numbered) which raise the garage door 46.
U.S. Pat. No. 4,852,706 to Pietrzak et al, dated Aug. 1, 1989 and entitled “Gate Operator”, discloses a gate operator including, as illustrated in FIGS. 3, and 5, a clutch assembly 32, a clutch operator member assembly 50 and a clamp head 52. The clutch assembly 32 includes worm wheel 30 and floating pressure plates 34, which drive pressure plates 36 and friction discs 38 and thus drive sprocket 18. Clutch operator member assembly 50 includes Bellville washers 49, collar 58, needle bearing 60 and thrust washer 62. Clamp head 52 is operated by a lever 54 controlled in turn by a screw 70. In operation, the clamp head 52 functions to engage the clutch operator member assembly 50 for tensioning the clutch assembly 32. For example, when it is desired to tension the clutch to increase the load at which the clutch will slip, screw 70 is adjusted whereby clamp head 52 is pivoted causing thrust washer 62 to apply pressure to collar 58. This pressure causes Bellville washers 49 to apply pressure between the various plates of the clutch assembly 32. The gate operator pulls chain 86 to open and close the gate. Clutch operator member assembly 50 may be used to manually engage and disengage clutch assembly 32.
Known swing door operators usually have a type of door closer which automatically closes the door in a power failure. Prior art door openers also include those which are movable only when energized. These devices suffer from the drawback that upon loss of power the door is not easily movable, creating a hazard in the event of a fire. Some require sensors mounted in the motor housing or drive shaft to sense stoppage of the doors by an obstacle, and to disengage the clutch or stop the motor so as to prevent damage to the device or obstacle. Some have a clutch mechanism which must be operated manually.
Accordingly, it is desired to provide a door opener which may open a conventional side hinge door. It is also desired to provide a door opener which allows the door to stop when an obstacle is encountered, without the use of expensive, unreliable sensors, switches, torque controls and the like. It is also desirable to provide an automatic door opener that is easy to retrofit to existing doors and that provides an easily adjusted range of motion.